Thermocolor ribbons known in the prior art comprise a support foil of paper, plastic or the like having a fusible color layer coating at least a portion of one side of the support foil. The fusible color layer may include a wax-bound coloring or carbon-containing substance (pigment).
Thermocolor ribbons are used in thermal printing processes in which a heated printer head presses the thermocolor ribbon to a paper transferring the character or design on the printer head to the paper. Examples of thermal printers or printing processes can be found, for example, in German Pat. Nos. 2,062,494, 2,406,613 and 3,224,445.
More specifically, thermocolor ribbons function in thermal printing devices as follows: A heated printer head is pressed against a thermocolor ribbon and a paper. The thermocolor ribbon's uncoated side comes into direct contact with the heated printer head on which raised print symbols or designs are found and its coated side contacts the paper. During the printing proces there is no relative motion of the paper with respect to the thermocolor ribbon so that the printer head which is heated to temperatures of around 400.degree. C. melts or softens a part of the fusible color layer forming the desired print character or design. The softened or melted part of the color layer forming the desired print is transferred to the paper on contact between the thermocolor ribbons and the paper during the printing process. The thermocolor ribbon is removed from the paper or other substrate generally by a take-up spool following the actual transfer of color by adhesion. Unfortunately print characters obtained using the thermocolor ribbons of the prior art lack the sharpness and definition required of printed characters. Furthermore, smearing may occur during the printing process. Also the printing apparatus may become jammed-up by accumulation of unwanted residues from the thermocolor ribbon.